Method of preparing aralkylated phenolic compounds



METHGD OF PREPARING ARALKYLATED PHENGLIC COIVIPOUNDS No Drawing. Application May 23, 1950, Serial No. 163,808

6 Claims. (Cl. 260-619) This invention relates to the preparation of aralkylated phenolic compounds and more specifically pertains to improvements in the method of preparing such compounds by the condensation of an aryl-substituted alkene hydrocarbon with a phenol.

Heretofore aralkylated phenolic compounds have been prepared by the condensation of phenols with aryl-substituted alkene hydrocarbons such as styrene, and alphamethyl styrene using, as condensation catalysts, such powerful catalysts as anhydrous aluminum chloride, boron trifluoride, concentrated sulfuric acid, and phosphoric acid or hydrogen halide catalysts such as hydrogen chloride or hydrogen bromide eiher per se or in aqueous solution. The yields of aralkyl ated phenolic compounds obtained when using the-powerful catalysts have been quite low due to formation of by-products, polymerization of the alkene hydrocarbon and other factors. Higher yields are said to be secured when hydrogen halide catalysts are used'but it has been my experience that such catalysts likewise produce. low yields. In addition the products obtained using theseknown catalysts are often badly discolored and are otherwise not completely satisfactory for some uses, particularly for use as rubber antioxidants as disclosed in my copending application Serial No. 163,806filed May 23, l950, now Patent No. 2,670,340. r 3 r .I have discovered thatnuclear aralkylat ed phenolic compounds can be prepared in high yields 'withou t any of the above-mentioned disadvantages by condensing .a phenolic compound with an aryl-substituted alkene hydro: carbon in the-presence of either dilute aqueoussulfuric acid or ahydrocarbon sulfonic .acid, as the condensation catalyst. v

The condensations carried out according .to this invention progress smoothly to substantially 100% completion Without violence and without substantial formation of by-products. Best results are secured when operating at nited States Patent is maintained at the desired reaction temperature.

In the preferred range of the catalyst, one to two pounds of the catalyst for each pound mole of the hydrocarbon reactant or one to two grams of the catalyst for each gram mole of the hydrocarbon reactant are the particularly preferred proportions of the catalytic materials to be used.

The condensation process of this invention is preferably carried out in the following manner. The catalyst and the phenolic compound (or a solution thereof in an inert solvent) are added to a reaction vessel equipped with a stirrer, a reflux condenser open to the atmosphere, a charging line, and means for heating and cooling the reaction mixture. The phenolic compound and the catalyst are heated to the reaction temperature and then the hydrocarbon reactant is added slowly to the reactor with stirring during which time the temperature The resulting reaction mixture is then cooled, diluted with an atmospheric pressure and when the temperature of the reacting mixture is maintained at or about (within 120 C. of) the boiling point of the most volatile component of the reaction mixture, which is generally the hydro carbon reactant and possesses a boilingpoint of 140 C. to 200? C. Hence a satisfactory operating temperature range is generally from 120" C. to 2 20 C. when'operating at atmospheric pressure. Temperatures as high as 300 C. can be employed when the condensation is carried out at pressures in excess of atmospheric pressure. Temperatures as low as C. can also be used'when the reaction is effected in presence of a low-boiling inert solvent or diluent (as is sometimes desirable if the phe= nolic reactant is a solid), itbeing understood that temperature is not a critical factor in theinvention.

The amount of catalyst to be used according to this invention is quite small. In general an amount of catalyst from 0.01 to 5% by Weight of the hydrocarbon reactantis employed withthe preferred amount being /2 to 2 parts by Weight for each molar part by weight of the hydrocarbon reactant. t

inert liquid such as benzene if necessary to reduce its viscosity, and then washed free of acid with an aqueous solution of an alkali. such as sodium carbonate. The resulting washed mixture is distilled at atmospheric pressure to remove diluents, unreacted hydrocarbon and unreacted phenol, if any of these are present, and the distillation is then continued at reduced pressure to recover .the condensation product. The nuclear aralkylated phenolic compounds formed during the condensation reaction can be recovered in a single fraction consisting generally of a mixture of individual compounds or, if-desired, substantially pure individual compounds can be recovered by further fractionation at reduced pressure.

The sulfonic acids which can be employed as condensation catalysts according to this invention possess the structure R-SO3H where R is hydrocarbon and include, for example, such aryl sulfonic acids as benzene sulfonic acid, toluene suifonic acids, xylene sulfonic acids, ethylbenzene sulfonic acid, mesitylene sulfonic acid, pseudocumene sulfonic acid and alphaand beta-naphthalene .sulfonic acids and such alkane sulfonic acids as ethane sulfonic acid, methane 'sulfonic acid, propane sulfonic acid, butane sulfonic acid and the like. In addition,

dilute aqueous sulfuric acid containing from 25% to-5 0% by weight of H2804 can also be used as catalyst for the condensation reaction.

Among the phenolic compounds which can be employed in the condensation reaction of this invention there may be mentioned phenol, cresols, p-octyl phenol, pyrocatechol, resorcinol, hydroquinone, pyrogallol, hydroxybiphenyl, phloroglucinol, alpha-naphthol, and betanaphthol. All these compounds possess the structure Ar-(0H),. wherein Ar is an aromatic hydrocarbon radical having its connecting valences on nuclear carbon atoms, and n is an integer from to 1 to 3. Other phenols of this structure are equivalent to those specifically named and can, of course, also be used.

Any aryl-substituted alkene hydrocarbons (also called aralkylene hydrocarbons) can be employed in the condensation process of this invention. Such compounds will, of course, contain an aryl radical connected to .an aliphatic carbon chain in which there is'an olefinic double bond. The preferred aralkylene hydrocarbons are those of the structure i wherein AI is aryl and R is hydrogen or 'alkyl among which there may be mentioned styrene, alpha-methyl styrene, alpha-ethyl styrene, p-methyl styrene, p-isopropyl styrene, p-methyl-alpha-methyl styrene, betamethyl styrene, vinyl naphthalene and the like. Qther arm-substituted alkene hydrocarbons which may be present.

used are Z-methallyl benzene, 2-methyl-1,1-diphenyl propene 2, 'allyl benzene, 'allylnaphthalene, 1---phenyl propene-2 and the like.

The following specific examples wherein specific pheno'lic'compounds and aralykylene hydrocarbons are employed as reactants will illustrate the condensation process of this invention. The term parts is employed in the examples to designate parts by weight.

EXAMPLE I To a reactor equipped with a stirrer, a thermometer, a reflux condenser, means for heating and cooling-its contents, and -a charging line, there -was added 5 parts of "p-toluene sulfonic acid monohydrate and '141 (1.5 moles) parts of phenol. This mixture was heated to about 140C. and then 312 (3 moles) parts of styrene were added over "aperiod of two 'hours'while the reaction temperature was maintained-at 140" i 5 'C.

The reaction mixture was cooled toabout 70 C., then an aqueous solution containing 5% 'by weight of sodium carbonate and 10% salt was added with stirring to neutralizethesulfonic 'acid. The-reaction mixture was then diluted with 150 parts otbenzene. A -sharp separation between the 'benzene solution and the aqueous solution was obtained when the mixture :of the colorless benzene and water solutions was allowed'to settle.

The benzene solution was washed with water "and then charged to a still pot. Benzene and entrapped'water-were removed by distillation at atmospheric pressure. Then the pressure was reduced slightly on the still and unreacted phenol and styrene wereremoved. About 8 parts of a mixture of phenoland styrene, principally'phenol, were recovered. There'wasalso'about two parts of phenol in the aqueous mediums employed to neutralize" the acid catalyst and to wash the benzene solution. There was no dimer or polymer of styrene The material remainingin the still pot, a. mixture of colorless styrylated phenol compounds, was fractionated at reduced pressure. A total of-443 parts, a-98'% yield, of three colorless products were obtained by this fractionation. The three products,"the amount and percent-of total of each product, physical properties of--each product, as well as the chemicalname given to eachproduct after identification are tabulated below. l

Table I f-Product ggf Percent .Physical Propertiesi Identified As- I -Q. -'62 14. Oil, 13. P. 112" to '4(1-phenyl-l'-eth- 141 .0. at 0.45 to yl);phenol. 0.55 mm. 11 219 49. 4 Viscous Oil, B. P: 2,4 di-(1-phenyl-1- 149 C. to 195 ,O. ethyl) phenol. at 0.45 to 0.55 mm. III 162 "36. 6 Very Viscous Oil, B. 2,4;6-tri (1=phenyl- P. 202 to 208 C. at l-ethyl) phenol.

EXAMPLE II The process of Example I was repeated except that "-parts of ethane sulfonic acid monohydrate were used as a catalyst. "A -90% yieldofamixturenf the three aralkylated='phenols, themono-, 'diand tri-(l phen'yl-lethyl) "phenols, was obtained.

EXAMPLE III EXAMPLE IV :141 parts of phenol and 3l2.parts of styrene, .aratio :of 2..moles of styrene foreach mole ofphenol, were condensed in the presence of 8.0 parts of 25% by weight sulfuric -acid-employing thesame procedure as described in Example I. The resulting mixture was neutralized with aqueous sodium carbonate, diluted with benzene and washed with water. There was no difiiculty experienced in separating the aqueous layer from the colorless benzene solution.

The neutralized, washed benzene solution was charged to a still pot and'the benzene was distilled oil at atmospheric pressure. Then the mixture in the still pot was distilled "at .a slightly reduced pressure and 4.3 parts of unreacted phenol was recovered. (An additional 1.9 parts of unreacted phenol was extracted by the aqueous washes.) -No styrene, styrene dimer or polymer was present. The remaining mixture, 451.1 parts, a 99.6% yield was fractionallydistilled at ;reduced pressure, from 0.4 to 0.55 mm., and three colorless products were obtained. These three products in the order of their volatility were 60.1 parts (13.5%) of 4-(l-phenyl-l-ethyl) phenol, 211.1 parts (47.2%) of 2,4-di-(1-phenyl-1- ethyl) phenol, and 175.6 -parts (39.3%) of 2,4,6-tri- 1=phenyl-1'-ethyl) phenol.

E M L V -l"41 parts -of phenoland 354 -parts of alpha-methyl styrene were condensed at li-5 C. in the presence of 5 parts -of'p-toluene sulfonic acid-monohydrate by the {procedure describedin-Example I. The acid catalyst-wasneutralized'with sodium-carbonate, benzene was addedto dilutethe-reaction'mixture and the colorless benzene-solution was-washedwith water as described in 'Example I. The benzene-solution was charged into a'still-pot and'the'benzene with entrapped water was removed-at-atmospheric pressure. Then the distillation equipment was subjected to "-a slightly reduced pressure to--rernove unreacted phenol-and-alpha-methyl styrene. No phenol was-rec0vered,but 9.0 parts of alpha-methyl styrene-and 3125- parts of-dimers of alpha-methyl-styrene were recovered. *There remained in the distillation equipment 441;parts, 'a yield of 89%, of phenol aralkylated. to--various degrees. The components were separated and recoveredbydistillation 'at-reducedpressure from 0.4 to"0;5 mm. 'The 'firsrfraction-removed had a-boiling point of 135 C. at 0.45 mm. This material crystallized on cooling to'white crystals which had a melting point of 75 to 77 C. and was identified as -4(1-phenylisopropyl) phenol. Thesecond'fractionhad a boiling point of 180to1*85 'C.- at'0'.5 -mm., also'crystallized to white crystals of a melting point of 65.5 to 67 C. This second fraction was identified as'2,4-di-(1-phenylisopropyl) phenol. The residue, the third component, crystallized to-white crystals of a melting point of 141 to 142 C. and was identified as 2,4;6-tri-(1-phenylisopropyl) phenol. 'Of' the aralkylated phenols produced by this condensation 109.3 parts(24.8%) were monosubstituted.phenol,'298t6 parts (67.7%) were the disubstitutedphenol and 33.1 parts (75%) were the trisubstituted'phenol.

. :EXAM'PLE'VI The; condensation: processof Example .V was changed only-byssubstituting 4. ,parts of :50%: Sulfuric acid as the catalyst in place of the toluene sulfonicacid. Otherwise the-amountofi reactants, the condensation reaction, reactiontemperaturq; and. the recovery steps were the same as ,described in Example III. A 90.5% yield, 448.3 parts of:aralkylatedphenolwere recovered. .Of this 157.2 parts or35.l% :were.4-(1-phenylisopropyl) phenol, 267 parts or 59.6% :.were .2,4=di-(l-phenylisopropyl) phenol, and 24.1 parts of 5.3 a-Were ..2,4.,6-tri-( l-phenylisopropyl) phenol. -No unreacted phenol-remained .after the .condensation, but 25.6 parts, 7.2% of the alphamethyl styrene were recovered as the; dimer.

The'above; examples show that very high yields of exeellentaralkylated phenol productsare secured in accordance with this invention. ,,This-,is,not;thecase, howare ever, whenusing the condensation catalysts heretofore known. For example wh'en the procedure and reactants of Examples V and VI were employed using 95% concentrated sulfuric acid 'as' catalyst, 'no separation of the from acid salts and then charged to a still pot where elitrapped water and benzene. were distilled off at atmospheric pressure. The materials remaining in the distillation equipment were subjected to reduce pressure but aqueous solution and the benzene solution was possible no m-cresol, styrene or dimer of styrene distilled off. because of formation of an emulsion due to the presence There remained 455.6 parts, a yield of 93%, of aralkylated of sulfonated products. Working up of the reaction m-cresols. On fractionation a first fraction of 41.1 parts product was therefore quite diflicult. Moreover, the re- (9.2%) was recovered at a temperature of 175 to 183 action product contained only a 75% yield of aralkylated C. at 0.75 mm. and was identified as 5-methyl-2-(1- phenols, there also being present a considerable quantity phenyl-l-ethyl) phenol, an'da second fraction of 369.4 of dimerized alpha-methyl styrene, as well as unreacted parts (81%) was recovered at 189 to 196 C. at 0.75 phenol. In addition, when-the procedure and reactants mm. and was identified as 5-methyl-2,4 (or 2,6) di-(lof Examples I and- V-were employed using anhydrous phenyl-l-ethyl) phenol. Fromthe residue remaining in aluminum chloride, boron trifluoride and hydrogen chlothe still pot there were recovered 44.6 parts (9.8%) of ride respectively as catalysts, yields helow50% of arala very viscous, high boiling material identified as 3-methylkylated phenols were obtained. In each case large 2,4,6-tri-(l-phenyl-l-ethyl) phenol. amounts of by-products were present in the condensai 4 1 tion product and even the aralkylated phenols which were EXAMPLE IX secured were so discolored as to be of considerably less I I a imila anner 216 parts of beta-naphthol' were value as antioxidants than the products of Examples I condensed i h 312 f styrene at 140 5 C i h and V. I presence of 5 parts of p-toluene sulfonic acid. The yield EXAMPLE VII of aralkylated naphthols after removing the catalyst and 177 parts of p cl.eso1 and 312 parts of Styrene were unreacted materials was 467.4.parts, a yleld of 88.5%. condensed at 140:5" C. in the presence of 5 parts of P s an l mammal were recovered y p-toluene sulfonic acid employing the procedure described dlstlllsnon at 187 at to Thls in Example I. The acid catalyst wa s neutralized with matenal was ldsnflfied as sodium carbonateand'the reaction mixture was washed 11101" remamufg ss 3905 Parts was free of resulting sodium salts after dilution with benzene. very s s s hlgh bqllmg and was sublected to Then the benzene solution was charged to a still pot fsrther By mfi F q a ultra where the benzene was distilledofi at atmospheric press absorptlon was determmed that thls {esldue was sures. No unreacted 'styre'n'e', dimer of styrene or unreact- 'substltuted naphtholbut the Pomt of ed p-cresol distilled over when the mixture remaining after stltutlon of thesecond aralkyl group (l'phesyll'ethyl) removal of benzene was heated at slightly reduced preswas not determmed' I sure. There then remained 460 'parts, a yield of 94.5%, EXAMPLES X o XIII. of aralkylated cresol in the distillation equipment. Of a a A this 15.1 parts (3.2%) of an oily liquid having a boiling These examples Were carried out according to the propoint of 180 to 185 C. at 0.75 mm. and identified as cedure describedinExample I, but the specific details have 2-( l-phenyl-l-ethyl)-p-cresol, 437.5 parts (92.4%) of a been consolidated in tabular form for simplification.

Table II ARALKYLATION 0F PHENOLIC COMPOUNDS Reactants-Parts Q EP E Catalyst, Parts ggfgg ig gg Percent Physical Properties Phenolic Aralkylene 4-(1-p-tolylisopropyl)-pheno1 23.6 B. 141143 C.

. mm. 2,4-di-(l-p-tolylisopropyl) phenol 69.7 B. P. 195 C. X phenol, 141 alpha, para-dime 140:1:5 p-toluene sulionic @0.5 mm.

parts. thyl styrene, 396 acid monohy- 2,4,6 tri (i-p-tolyiisopropyl) 6.7 exceedingly viscousparts. drate, eparts. phenol. High boiling at 0.5

mm. 2,- (l-phenylisopropyl) -p-cresol 55.5 B. P. 118122 O.

0.7 mm. 2,6 di (1 phenylisopropyl) p- 41.8 B. P. 182 C. XI p-cresol, 177 a1pha-methyl sty- 140:1:5 do cres @0.8 mm.

parts. rene,354 parts. 2,3,6(or 2,5,6)-tri-(1-phenylisopro- 2.7 Very viscous liquid pyl)-p-cresol. ang8 high boiling mm. 2-(1-phenylisopropyl) -5-methy1 73.8 B. P. 123-150 C.

phenol. @0.75mn: 1 a XII m-cre sol, 177 do 140:1:5 do gf %igg%'f s par Tri (i-phenylisopropyl) 5 0.5 Highboiling@0.8mm.

methyl-phenol. -(1-phenylisopropyl)-2-napthol... 73 B.@ (15.76 180190 C.

. mm. XIII--"- g 05:5 Di-(l-phenylisopropyl)-2-naphthol- 27 Very viscous oil. Hig 1 par boiling at 0.75 mm.

viscous oily liquid boiling at 189 to 190 C at 0.75 mm. and identified as 2,6-di-(l-phenyl-l-ethyl)-p-cresol, and 8.3 parts (1.8%) of a high boiling material, tri-( 1- phenyl-l-ethyl)-p-cresol, were recovered.

EXAMPLE VIII 177 parts of m-cresol and 312 parts of styrene were condensed at l40i5 C. in the presence of 5 parts of p-toluene sulfonic acid employing the procedure described in Example I. The acid catalyst was neutralized with sodium carbonate and the reaction products were diluted with benzene. The benzene solution was washed free 

1. THE METHOD OF PREPARING ARALKYLATED PHENOLIC COMPOUNDS WHICH COMPRISES CONDENSING A PHENOLIC COMPOUND WITH AN ARYL-SUBSTITUTED ALKENE HYDROCARBON HAVING THE FORMULA 